Background: Diagnosing hyperkeratotic lesions on the palms and soles is often challenging for both clinicians and pathologists. Interleukin (IL)-36 cytokines play an important role in the pathogenesis of psoriasis.
Methods: We retrospectively re-evaluated hematoxylin-eosin-stained biopsy specimens of 30 patients with clinically diagnosed palmoplantar psoriasis (PP) and 30 patients with palmoplantar eczema (PE), and then performed IL-36α and IL-36γ immunohistochemistry.
Results: Among the histopathologic features, thinning of the rete ridges and vertical alternation of parakeratosis and orthokeratosis had the highest positive predictive value (PPV) in diagnosing PP (72.7% and 69.3%, respectively). Immunohistochemically, patients with PP predominantly showed diffuse or focal strong expression with IL-36α and IL-36γ staining in the upper layers of the epidermis (86.7% and 83.3%, respectively). The comparison of the mean IL-36α and IL-36γ expression scores significantly differed between PP and PE (P < .001). Among all histopathologic and immunohistochemical features, diffuse strong expression of IL-36α and IL-36γ staining had the highest PPVs in favor of a diagnosis of PP (75% and 76.7%, respectively).
Conclusions: Our data suggest that IL-36α and IL-36γ immunohistochemistry can be used in the differential diagnosis of PP and PE.
Keywords: IL-36α; IL-36γ; immunohistochemistry; palmoplantar eczema; palmoplantar psoriasis.
© 2021 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.